Dental amalgam

ABSTRACT

AN IMPROVED DENTAL AMALGAM CONTAINING ONE TO TEN PERCENT BY WEIGHT OF GALLIUM FOR ADHESION OF THE AMALGAM TO THE TOOTH SURFACES.

United States Patent US. Cl. 75-134 3 Claims ABSTRACT OF THE DISCLOSUREAn improved dental amalgam containing one to ten percent by weight ofgallium for adhesion of the amalgam to the tooth surfaces.

This invention relates to an improved dental amalgam and in particularan amalgam to which gallium is added to result in adhesion to the toothstructure.

Dental amalgam or the so called "silver filling commonly used to fillteeth has the following approximate composition in percentage by weight:

Percent Silver 33.0 Mercury 52.0 Tin 12.5 Copper 2.0 Zinc 0.5

In making fillings with amalgam care must be taken to avoid moisturewhich may come from perspiration on the hand or from the mixingequipment. Moisture will cause excessive expansion and weakening of thehardened alloy. Excess mercury, remaining in the alloy after packingcauses excessive expansion and flow. Excessive working of the alloyduring amalgamation or packing reduces the expansion which normallyoccurs. Incomplete amalgamation results in a filling which corrodesreadily. Incomplete packing increases corrosion and decreases thestrength of the filling.

These and other diificulties are recognized by dentists and considerableskill arid experience is required to produce amalgam fillings which arereasonably satisfactory. In this connection reference may be made to abooklet on the subject by Wilmer Souder and George C. Paffenbargerentitled Physical Properties of Dental Materials, published by the US.National Bureau of Standards as Circular C 433, 19412.

The most serious limitation to conventional amalgam fillings is thatthere is no adhesion to the tooth surfaces. In the absence of adhesionto the tooth surface fillings made with conventional amalgams are heldonly by mechanical means. In practice it is necessary to undercut thecavity so that the amalgam filling will be locked in mechanically. Thisrequires additional drilling and unnecessary removal of the toothstructure so that the amalgam filling is mechanically wedged or lockedin. This also weakens the tooth unnecessarily so that chipping,fracturing and loss of the tooth commonly occurs.

We have found that the addition of about 3% gallium to the amalgamresults in adhesion to the tooth structure. This eliminates much of thedrilling which has heretofore been found to be necessary withconventional amalgam fillings. It has been necessary up to now to drilla convex cavity to lock in the conventional amalgam fillings. We findthat a concave cavity can be filled with the present amalgam due toadhesion to the tooth structure. Also the present invention provides forstronger and longer lasting fillings.

It is therefore an object of this invention to provide rce for animproved dental amalgam which is characterized by good adhesionproperties to the tooth surfaces.

It is also an object of this invention to eliminate undercutting andunnecessary drilling of teeth which has been the practice of the priorart with the amalgam fillings heretofore available.

It is also an object of this invention to accomplish these advantageswith an improved amalgam alloy which has satisfactory strength,corrosion resistance, conductivity, density, and expansion.

While very satisfactory fillings with good adhesion and good packingcharacteristics have been made with an amalgam containing about 3%gallium, we have found that up to about 10% gallium can be used topromote adhesive properties to the amalgam.

Therefore the preferred composition range of the present improvedamalgam is as follows, all percentages being by weight:

Range, percent Silver, 32.0% 30 to 34 Mercury, 50.5% 48 to 52 Tin, 12.1%11 to 13 Copper, 1.9% 1.5 to 2.5 Zinc, 0.5% .25 to .75 Gallium, 3.0% 2to4 Also a broader composition range which has been found to besatisfactory is as follows, all percentages being by weight:

Percent Silver 25 to 3'5 Tin 10 to 14 Mercury 45 to 54 Copper 1 to 3Zinc Up to l Gallium 1 to 10 A more limited investigation indicates thatother similar elements in Group III of the Periodic Classification ofthe elements including indium and thallium can be added to dentalamalgam with or without gallium to result in adhesion of the filling tothe tooth surfaces. For a description of the Periodic Classification ofthe elements and the Group III elements including gallium, indium andthallium, reference may be made to a book entitled Elements of PhysicalMetallurgy, by A. G. Guy, copyright 1959, published by the AddisonWesley Publishing Co. Inc., Reading, Mass.

Having described our invention, it will be understood that the inventionmay be otherwise embodied within the scope of the following claims.

We claim:

-1. An improved dental amalgam containing the following approximatecomposition by weight:

Percent Silver 32.0 Mercury 50.5 Tin 12.1 Copper 1.9 Zinc .5 Gallium 3.0

2. An improved dental amalgam for filling non-convex cavities, the saidamalgam being characterized by good adhesion to the surfaces of the saidcavities; the said amalgam containing the following approximatecomposition by Weight: silver 30 to about 34%; mercury 48 to about 52%;tin 11 to about 13%; copper 1.5 to about 2.5%; zinc 0.25 to about 0.75%;and gallium 2 to about 4%.

4 3. An improved dental amalgam characterized by ad- References Citedhesion of the said amalgam to the tooth surfaces, said UNITED STATESPATENTS amalgam containing the following approximate composition byWeight: 1,963,085 6/1934 Gray 75l73 Percent 2,629,656 2/1953 Lyle 75l73S'l 30 t 34 ilia 48 52 L. DEWAYNE RUTLEDGE, Primary Examiner Tin 11 to13 ERNEST L. WEISE, Assistant Examiner Copper 1 /2 to 2 /2 Zinc 1A to 10US. Cl. X.R.

Gallium 1 to 10 173 UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION 3,554,738 Dated January 12, 1971 Patent No.

Victor E. Beldham et a1 Inventor(s) It is certified that error appearsin the above-identified paten and that said Letters Patent are herebycorrected as shown below:

In the heading to the printed specification, lines 3 t "Victor E.Beldham, 552 Arizona Drive New Kensington, Pa. 1 and Richard F Harvey,5527 Old Carriage Lane, Orchard Lake, Mich. 48033" should read Victor EBeldham, New Kensingto Pa. and Richard F Harvey Orchard Lake Michassignors t Metaltronics Inc Orchard Lake, Mich. a corporation ofPennsylvania.

Signed and sealed this 7th day of September 1971 (SEAL) Attest:

EDWARD M. FLETQHER,JR. ROBERT GOTTSCHALK Attestlng Offlcel" ActingCommissioner of Pat

